1. Field of the Invention
The present invention relates generally to the treatment of bio-oil. More specifically, the invention concerns processes and systems for reducing residual and bound water in bio-oil.
2. Description of the Related Art
With its low cost and wide availability, biomass has increasingly been emphasized as an ideal feedstock in alternative fuel research. Consequently, many different conversion processes have been developed that use biomass as a feedstock to produce useful biofuels and/or specialty chemicals. Existing biomass conversion processes include, for example, combustion, gasification, slow pyrolysis, fast pyrolysis, liquefaction, and enzymatic conversion. One of the useful products that may be derived from the aforementioned biomass conversion processes is a liquid product commonly referred to as “bio-oil.”
Despite recent advancements in biomass conversion processes, many of the existing biomass conversion processes produce low quality bio-oils containing high amounts of bound water. “Bound water” is water that is physically and/or chemically bound within the bio-oil so that it does not naturally separate from the bio-oil. Bio-oils containing high amounts of bound water are not readily miscible with hydrocarbons due to their high polarity and, thus, require extensive secondary upgrading in order to be utilized as transportation fuels, petrochemicals, and/or specialty chemicals. Additionally, the bound water in these low quality bio-oils tends to increase the amount of organic acids present in the bio-oil, thus increasing its corrosive nature and diminishing its ability to be stored over long periods of time. Furthermore, these low quality bio-oils tend to readily degrade over time due to polymerization of the bio-oil caused by its highly corrosive nature.
Bio-oils may be subjected to various separation processes in order to remove bound water. These processes, which have utilized distillation columns and/or molecular sieves, expose the bio-oil to unfavorable conditions in order to extract bound water. Such conditions facilitate polymerization of the bio-oil, thus increasing its viscosity and lowering its usefulness as a fuel. Consequently, previous separation processes have degraded bio-oils in the attempt to remove bound water.
Accordingly, there is a need for an improved process and system for removing bound water from bio-oil.